SBC Overheating

OK Gentlemen I have a friend with a problem we can't figure out. 350 crate motor in a Jeep CJ with a TH350 auto and 2500 stall convertor. This thing overheats at two blocks of driving, I mean 260 degrees. He's replaced waterpump, thermostat, intake manifold, radiator, and has electric fan with shroud. Fan is a puller and rated at 1700 cfm. Any ideas???

One thing you might check is pump direction....sometimes pumps will work reversed if it was originally intended to be used with serpentine belt. If the builder made a serpentine into a v belt operation, the pump, although new, will not pump well running backwards. You may even see some water flow looking into the radiator but it won't cool very well. Don't ask me how I know this....

Usually, a reverse pump will have a large R embossed on the pump...

me too

I had a built 283 in a 64 j10. I removed the thermostat and that helped but not enough. An older hot rod buddy looked in to radiator and decided not enough water flow. Replaced water pump to no help. End of story took motor down and used a wire brush on a drill and cleaned out all water passages. End of problems. We also added a fan shroud too.

Yeah...kind of a myriad of things it could be...

a check of all the basics...I've seen some really weird stuff....but as was said, check pump and fan / fans for proper rotation...if electric and a puller is it really pulling....usually if you remove a thermostat I've found that it circulates water too fast thru the radiator at road speed...will overheat...also seen water pump impellers that are not turning...spun on the shaft and or fell off....could go on and on...(usually do)...but lots of things to check...JMHO...

Cracked head

What about bad timing. The timing gears could be out two or three teeth. You can hear the exhaust note is wrong if the distributor is out but I don't know if you can hear the valves out of time.

if it over heats in 2 blocks of driving, it has to be crack somewhere.

combustion gasses are the only way you can overheat the cooling system that fast.

or you have one big A$$ air pocket in the cooling system.

Is the water actually circulating? I think exador is onto something, you might have a blocked water passage.

Iv'e seen these with the small hole to the rear put on backwards.

Is it a new crate motor?

Old Iron said:

Cracked head

Click to expand...

Who you calling a crack head??

sgtpontiac said:

Who you calling a crack head??

Click to expand...

[cl[ddd

sgtpontiac said:

Who you calling a crack head??

Click to expand...

[cl

Thanks for the ideas. It has a serpentine belt setup with reverse waterpump which has been replaced twice. Timing has been checked many times and it is a new crate motor from GM. Not sure if he's checked for cracked head as it's a new motor. Will ask about intake gasket. He thought the first intake had a crack in crossover but changing intakes didn't help. He's checked everything suggested so far. Any other ideas?

just make sure on the water pump being the right on, as you can use the serpentine belt with out the reversed pump. the only other thing that comes to mind is the top of the radiator being lower then the top of the motor causing a air pocket. might try to put the jeep on a step incline and check the water level to make sure it doesn't have the air pocket. it seems like the radiator set alittle low on a buddies jeep and that is what we did. i just can't remember if it was his cj or wagoneer. pics would help a lot.

I`d have the CO level in the coolant checked . That way you know if it`s burning coolant. I`d check torque on the head bolts too... seen a crate motor or two with loose bolts....

As it was a crate motor, was there a plastic plug in the cooling system that wasn't removed before installation? Stranger things have happened.

For it to heat up that fast it seems like there's no circulation.

Are you sure the temperature gauge reading is correct?

Does it heat up as quickly while idling (before driving)?

Thanks for all the ideas and suggestions. It's been determined that the problem has to be in the engine, So, He's replacing it with another engine he has. This should be interesting! 454 .030 over, roller cam, aluminum heads, and tunnel ram with 2 750 holley carbs. IN A JEEP CJ !!!

Let me know what kind of tires he's running so I can buy some stock in the company!